Electrical regulating apparatus including an ionic current regulator



Aug. 12, 1958 H. w. BRAcKNl-:Y 2,847,635

ELECTRICAL REGULATING APPARATUS INCLUDING AN IONIC CURRENT REGULATOR med Feb 4. 194e Q) INVENTOIL 7K award Wvrafckne ELECTRICAL APPARATUS IN- CLUDKNG AN lNitC URRENT REGULATOR Howard W. iiraclrney, Galt Ridge, VKenn., assigner, by mesne assignments, to the United States of America as represented by the United States Atomic Energy Commission Application February 4, 1946, Serial No. 645,458

Claims. (Cl. 323-20) This invention relates to apparatus for separating charged particles, such as ions, by utilizing the magnetic mass spectrum thereof and more particularly to a control arrangement for regulating the operation of the apparatus.

One form of apparatus with which the invention is adapted to be employed comprises the combination of a partially evacuated closed vessel and a magnetic field of such strength as to constrain uniform velocity ions projected within the vessel to motion on circles having radii which are a predetermined fixed function of the momentum of the ions. By such means it is known that ions having a common origin and traveling different paths of equal curvature will, due to geometrical focusing action, substantially pass through a common region after 180 of travel.

In order for apparatus of the above type to have practical utility as a means of making isotopes available in quantity, it is necessary to collect separately the ions differing in mass i. e., the different isotopes, so that they may be recovered to provide materials having greater proportions of certain isotopes than occur in nature. When, as is usual, the isotopes are collected in properly positioned receiver pockets, it is important that the curvatures of the paths followed by the isotopes remain constant and this means that the magnetic field and the ion accelerating voltage must be constant. However, in practice, these factors cannot be held as constant as is desired although they are individually closely regulated and it has been usual to provide a tie-in between the two regulators so that changes in one can be compensated for by automatic change of the other. This tie-in is made sensitive to changes in the ion current received in one of the isotope collectors.

More specifically the tie-in regulator varies the percentage of the accelerating voltage applied to the regulator of the acceleration voltage in such a manner as to maintain one of the ionic currents constant at a predetermined value. Frequently during operation this tie-in or ionic current regulator cannot be used advantageously and at such times is turned off and it is an object of the invention to minimize disturbances in the accelerating voltage when the ionic current regulator is turned off.

Another object of the invention is the provision of a circuit arrangement whereby the ionic current regulator functions in its OFF position to furnish a voltage at approximately the middle of its regulating range.

Other objects and advantages of the invention will become apparent from the following description when read in connection with the accompanying drawing, the single figure of which is a schematic diagram incorporating one arrangement of the invention.

The arrangement shown in the drawing has been made largely diagrammatic and includes only those features necessary to a complete understanding of the invention. The various supporting structures and auxiliary equip- Jment may take any suitable form known to those skilled sa .fi Ind in the art and constitute no part of the present invention. Accordingly such structure and equipment have not been shown since it would serve to obscure rather than disclose the invention.

Referring to the drawing there is shown a closed vessel 10 positioned in a strong magnetic field provided by a magnet, one pole piece i1 of which is shown. The vessel iii provides a space Within which electromagnetic separation of ions may take place and is preferably highly evacuated although the presence of a small amount of gas is desirable under some circumstances to avoid so-called space charge effects.

Within the closed vessel 10 and also within the region of influence of the magnetic field produced by the pole piece 11, there is provided a source 12 of ions of a material the isotopesof which it is desired to separate and which, in conjunction with an accelerating electrode 13, serves to project in a direction normal to the magnetic field a stream or beam of high velocity ions. As is well known, these ions in traversing the magnetic field will be forced to follow circular orbits which result in the formation of the magnetic mass spectrum of the ions after approximately of travel from the accelerating electrede 13. These orbits are enclosed by a metal shield 14 to provide a field free space throughout their paths. lf, as is here assumed, `the ions consist primarily of two isotopes differing in mass, the ions of the greater mass will follow orbits having the curvature indicated by a path Q. Similarly, ions of less mass will describe orbits of stronger curvature indicated by a path R. For convenience all ions passing through the region of focus of the path R will be referred to as the R beam and the receiver 15 for this beam as the R pocket. Also, the ions passing through the region of focus of the path Q will be referred to as the Q beam and its receiver 16 as the Q pocket.

ln apparatus of this type using a known feed material in the ion source 12, the rate at which, for example, the ions in the R beam should be received in the R pocket 15 is readily determinable and the deionizing current to the R pocket thus is an indication of Whether or not the relationship between the strength of the magnetic iield and the accelerating voltage is correct.

The deionizing current to the R pocket 15 has been employed as a so-called R regulator to tie in the regulation of the magnetic field and the accelerating voltage and accompiishes its function by varying the percentage of the accelerating voltage applied to the regulator of the accelerating voltage. The complete arrangement is shown in the drawing as comprising a source of high voltage 17, which may be a rectifier, connected in series with a triode 15E, such as an S93 tube, across the ion source 12 and the accelerating electrode 13. In parallel with the source 12 and the electrode 13 is a voltage divider consisting of resistances 19, 20, 21 and 22 in series. A voltage regulator 23 connected across the resistance 19 functions to vary the resistance of the tube 1S in a manner to hold the voltage across the resistance 19 constant and as long as this voltage is a fixed percentage of the accelerating voltage i. e., the voltage across the electrode 13 and the ion source 12, the accelerating voltage will be held constant. However, if this voltage is not a fixed percentage of `the accelerating voltage, the regulator 23 will still hold constant the voltage across the resistance 19. This feature is the basis for the operation of the R regulator which will now be described.

The deionizing current to the R pocket 1S is caused to flow through a low resistance 24 to provide a. control voltage E., which is amplified by a suitable amplifier 25 and applied to the grid of a tube 26, here shown as type 897, to determine the plate voltage of the tube 26 and therefore the voltage across the resistances 21 and 22. This tube 26 and its associated power supply 27 from a D. C. input function to provide an output voltage across the resistances 21 and 22 which varies with variations in the current through the resistance 24 and therefore in accordance with the position of the R beam. These variations in the output voltage vary the percentage of the accelerating voltage which alects the voltage regulator 23 and thus, although the accelerating voltage has not changed, the regulator 23 senses a change and functions to correct it thereby returning the R beam to its proper position. It might be pointed out that the R regulator output as described above provides a bucking voltage the magnitude of which is indicated by a voltmeter 28 with its multipliers 29 and 30.

it frequently happens during operation of the apparatus that the R regulator cannot be used advantageously. ln accordance with the invention, Whenever the use of the R regulator is discontinued, it is arranged to provide an output voltage which remains constant at a mean value instead of zero as has been the practice. To change from regulation to standby a switch 31 is arranged to disconnect the grid of the tube 26 from the amplifier 25 and connect it between the resistances 21 and 22. When thus connected, the voltage across the resistance 22 is a feedback voltage E3 having an equilibrium value depending on the regulated bias voltage E1 and the grid voltage E2. Should the output voltage and therefore E3 tend to increase, E2 would decrease thereby increasing the plate current through the tube 26 which increases the drop across a load resistor 32 in the plate circuit of the tube 26, and the output voltage appearing across the resistances 21 and 22, though tending to rise, would be held virtually constant.

An important feature of the feedback circuit is the relative position of the switch 31 with respect to the condenser 33 bridging the cathode and a grid of the tube 26. With this condenser 33 connected as shown in parallel with a grid resistor 34, they have a time constant of preferably more than one second which prevents too quick a response and consequent oscillation when the switch 3l is moved to standby position 2.

From the above description it will be evident that when the switch 31 is in indicated position 1, the regulator is responsive to changes in the R current in a way which tends to keep the R current constant, and that when the switch 31 is in position 2 as shown, a portion of the output of the regulator is fed back into the grid circuit of the tube 26. This feedback voltage E3 will have an equilibrium value depending on the circuit constants and may have any desired value within the regulator range by properly proportioning the values of the resistances 21 and 22. In general, it has been found preferable to choose a value such that the regulator will stand-by at a voltage about the middle of its regulating range.

Although for the purpose of illustrating the invention a preferred embodiment thereof has been described in detail, it is to be understood that other embodiments are contemplated and that the scope of the invention is as deiined in the appended claims.

l claim:

l. In apparatus in which a load voltage is derived from a voltage divider having several segments in series, a primary voltage source connected across the divider, a regulator associated with the primary source for varying the magnitude of the source voltage to maintain constant the voltage drop across one of the segments of the divider, an auxiliary voltage source connected across another segment of the divider, means responsive to an operating condition of the apparatus for varying the magnitude of the auxiliary voltage within a known range, means responsive to a portion of the voltage drop across said other segment for maintaining constant the auxiliary voltage at a value substantially midway its operating range, and means for rendering the last-mentioned responsive means operative whenever the first-mentioned responsive means is rendered inoperative.

2. A voltage regulator adapted selectively to regulate in accordance with a rst signal voltage derived from its regulated voltage or in accordance with a second signal voltage not derived from its regulated voltage comprising, in combination, an electron discharge tube having at least a cathode, an anode and a control electrode, a two position switch one position of which connects said iirst signal voltage and the other position of which connects said second signal voltage to the control electrode, a resistor and a condenser in parallel directly across the cathode and the control electrode whereby the condenser has a charge regardless of the position of the switch, a voltage source, and means connected to said voltage source and responsive to the current ow through said tube for producing, as an output, the desired regulated voltage.

3. In apparatus in which a load voltage is derived from a voltage divider having a plurality of segments in series, a primary voltage source connected across the divider, a first voltage regulator means associated with the primary source and responsive to the voltage drop across one of the segments for varying the magnitude of the source voltage to maintain said voltage drop constant, an auxiliary voltage source connected across another segment of the divider, and a second voltage regulator means associated with said auxiliary voltage source and responsive to an operating condition of the apparatus for varying the magnitude of the auxiliary voltage.

4. In apparatus in which a load voltage is derived from a voltage divider having a plurality of segments in series, a primary voltage source connected across the divider, a first voltage regulator means associated with the primary source and responsive to the voltage drop across one of the segments for varying the magnitude of the source voltage to maintain said voltage drop constant, an auxiliary voltage source connected across another segment of the divider, and a second voltage regulator means associated with said auxiliary voltage source and responsive to a portion of the voltage drop across said other segment for varying the magnitude of the auxiliary voltage to maintain said last named voltage drop constant.

5. In apparatus in which a load voltage is derived from a voltage divider having at least three segments "in series, a primary voltage source connected across the divider, a first voltage regulator means associated with the primary source and responsive to the voltage drop across one of the segments for varying the magnitude of the source voltage to maintain said voltage drop constant, an auxiliary voltage source connected across another two of the segments of the divider, and a second voltage regulator means associated with said auxiliary voltage source and responsive to the voltage drop across one of said other two of the segments for varying the magnitude of the auxiliary voltage to maintain said last g named voltage drop constant.

References Cited in the le of this patent UNITED STATES PATENTS 2,239,768 Artzt Apr. 29, 1941 

